XindeX is an easy to learn and use application for creating, editing, and outputting indexes (e.g., for books). XindeX always shows the index in the correct order (there's never any need to explicitly sort). XindeX can automatically keep page numbers synchronized (e.g., for double-posting, or triple-posting, or more). Each XindeX index is stored in a single .xix file, so it is easy to backup or copy an index, and you can keep all your indexes in a single folder if you want. XindeX has far more conveniences and features than the few mentioned here.
Home Page - https://www.qtrac.eu/xindex.html